/Engine/Source/Editor/SequencerCore/Public/MVVM/Selection/SequencerCoreSelectionTypes.h
Select a key, optionally supplying a boolean to receieve a value indicating whether it was already selected or not
void Select ( [TViewModelPtr](API\Editor\SequencerCore\TViewModelPtr)< ModelType > InOwner, KeyType InKey, bool * OutNewlySelected )